/*
 * TokenMarker.java - Generic token marker
 * Copyright (C) 1998, 1999 Slava Pestov
 *
 * You may use and modify this package for any purpose. Redistribution is
 * permitted, in both source and binary form, provided that this notice
 * remains intact in all source distributions of this package.
 */

package org.syntax.jedit.tokenmarker;

import javax.swing.text.Segment;

/**
 * A token marker that splits lines of text into tokens. Each token carries a
 * length field and an indentification tag that can be mapped to a color for
 * painting that token.
 * <p>
 * 
 * For performance reasons, the linked list of tokens is reused after each line
 * is tokenized. Therefore, the return value of <code>markTokens</code> should
 * only be used for immediate painting. Notably, it cannot be cached.
 * 
 * @author Slava Pestov
 * @version $Id: TokenMarker.java,v 1.32 1999/12/13 03:40:30 sp Exp $
 * 
 * @see org.syntax.jedit.Token
 */
public abstract class TokenMarker
{
    /**
     * A wrapper for the lower-level <code>markTokensImpl</code> method that
     * is called to split a line up into tokens.
     * 
     * @param line
     *            The line
     * @param lineIndex
     *            The line number
     */
    public Token markTokens(Segment line, int lineIndex)
    {
        if (lineIndex >= length)
        {
            throw new IllegalArgumentException("Tokenizing invalid line: " + lineIndex);
        }

        lastToken = null;

        LineInfo info = lineInfo[lineIndex];
        LineInfo prev;
        if (lineIndex == 0)
            prev = null;
        else
            prev = lineInfo[lineIndex - 1];

        byte oldToken = info.token;
        byte token = markTokensImpl(prev == null ? Token.NULL : prev.token, line, lineIndex);

        info.token = token;

        /*
         * This is a foul hack. It stops nextLineRequested from being cleared if
         * the same line is marked twice.
         * 
         * Why is this necessary? It's all JEditTextArea's fault. When something
         * is inserted into the text, firing a document event, the
         * insertUpdate() method shifts the caret (if necessary) by the amount
         * inserted.
         * 
         * All caret movement is handled by the select() method, which
         * eventually pipes the new position to scrollTo() and calls repaint().
         * 
         * Note that at this point in time, the new line hasn't yet been
         * painted; the caret is moved first.
         * 
         * scrollTo() calls offsetToX(), which tokenizes the line unless it is
         * being called on the last line painted (in which case it uses the text
         * area's painter cached token list). What scrollTo() does next is
         * irrelevant.
         * 
         * After scrollTo() has done it's job, repaint() is called, and
         * eventually we end up in paintLine(), whose job is to paint the
         * changed line. It, too, calls markTokens().
         * 
         * The problem was that if the line started a multiline token, the first
         * markTokens() (done in offsetToX()) would set nextLineRequested
         * (because the line end token had changed) but the second would clear
         * it (because the line was the same that time) and therefore
         * paintLine() would never know that it needed to repaint subsequent
         * lines.
         * 
         * This bug took me ages to track down, that's why I wrote all the
         * relevant info down so that others wouldn't duplicate it.
         */
        if (!(lastLine == lineIndex && nextLineRequested))
            nextLineRequested = (oldToken != token);

        lastLine = lineIndex;

        addToken(0, Token.END);

        return firstToken;
    }

    /**
     * An abstract method that splits a line up into tokens. It should parse the
     * line, and call <code>addToken()</code> to add syntax tokens to the
     * token list. Then, it should return the initial token type for the next
     * line.
     * <p>
     * 
     * For example if the current line contains the start of a multiline comment
     * that doesn't end on that line, this method should return the comment
     * token type so that it continues on the next line.
     * 
     * @param token
     *            The initial token type for this line
     * @param line
     *            The line to be tokenized
     * @param lineIndex
     *            The index of the line in the document, starting at 0
     * @return The initial token type for the next line
     */
    protected abstract byte markTokensImpl(byte token, Segment line, int lineIndex);

    /**
     * Returns if the token marker supports tokens that span multiple lines. If
     * this is true, the object using this token marker is required to pass all
     * lines in the document to the <code>markTokens()</code> method (in
     * turn).
     * <p>
     * 
     * The default implementation returns true; it should be overridden to
     * return false on simpler token markers for increased speed.
     */
    public boolean supportsMultilineTokens()
    {
        return true;
    }

    /**
     * Informs the token marker that lines have been inserted into the document.
     * This inserts a gap in the <code>lineInfo</code> array.
     * 
     * @param index
     *            The first line number
     * @param lines
     *            The number of lines
     */
    public void insertLines(int index, int lines)
    {
        if (lines <= 0)
            return;
        length += lines;
        ensureCapacity(length);
        int len = index + lines;
        System.arraycopy(lineInfo, index, lineInfo, len, lineInfo.length - len);

        for (int i = index + lines - 1; i >= index; i--)
        {
            lineInfo[i] = new LineInfo();
        }
    }

    /**
     * Informs the token marker that line have been deleted from the document.
     * This removes the lines in question from the <code>lineInfo</code>
     * array.
     * 
     * @param index
     *            The first line number
     * @param lines
     *            The number of lines
     */
    public void deleteLines(int index, int lines)
    {
        if (lines <= 0)
            return;
        int len = index + lines;
        length -= lines;
        System.arraycopy(lineInfo, len, lineInfo, index, lineInfo.length - len);
    }

    /**
     * Returns the number of lines in this token marker.
     */
    public int getLineCount()
    {
        return length;
    }

    /**
     * Returns true if the next line should be repainted. This will return true
     * after a line has been tokenized that starts a multiline token that
     * continues onto the next line.
     */
    public boolean isNextLineRequested()
    {
        return nextLineRequested;
    }

    // protected members

    /**
     * The first token in the list. This should be used as the return value from
     * <code>markTokens()</code>.
     */
    protected Token firstToken;

    /**
     * The last token in the list. New tokens are added here. This should be set
     * to null before a new line is to be tokenized.
     */
    protected Token lastToken;

    /**
     * An array for storing information about lines. It is enlarged and shrunk
     * automatically by the <code>insertLines()</code> and
     * <code>deleteLines()</code> methods.
     */
    protected LineInfo[] lineInfo;

    /**
     * The number of lines in the model being tokenized. This can be less than
     * the length of the <code>lineInfo</code> array.
     */
    protected int length;

    /**
     * The last tokenized line.
     */
    protected int lastLine;

    /**
     * True if the next line should be painted.
     */
    protected boolean nextLineRequested;

    /**
     * Creates a new <code>TokenMarker</code>. This DOES NOT create a
     * lineInfo array; an initial call to <code>insertLines()</code> does
     * that.
     */
    protected TokenMarker()
    {
        lastLine = -1;
    }

    /**
     * Ensures that the <code>lineInfo</code> array can contain the specified
     * index. This enlarges it if necessary. No action is taken if the array is
     * large enough already.
     * <p>
     * 
     * It should be unnecessary to call this under normal circumstances;
     * <code>insertLine()</code> should take care of enlarging the line info
     * array automatically.
     * 
     * @param index
     *            The array index
     */
    protected void ensureCapacity(int index)
    {
        if (lineInfo == null)
            lineInfo = new LineInfo[index + 1];
        else if (lineInfo.length <= index)
        {
            LineInfo[] lineInfoN = new LineInfo[(index + 1) * 2];
            System.arraycopy(lineInfo, 0, lineInfoN, 0, lineInfo.length);
            lineInfo = lineInfoN;
        }
    }

    /**
     * Adds a token to the token list.
     * 
     * @param length
     *            The length of the token
     * @param id
     *            The id of the token
     */
    protected void addToken(int length, byte id)
    {
        if (id >= Token.INTERNAL_FIRST && id <= Token.INTERNAL_LAST)
            throw new InternalError("Invalid id: " + id);

        if (length == 0 && id != Token.END)
            return;

        if (firstToken == null)
        {
            firstToken = new Token(length, id);
            lastToken = firstToken;
        }
        else if (lastToken == null)
        {
            lastToken = firstToken;
            firstToken.length = length;
            firstToken.id = id;
        }
        else if (lastToken.next == null)
        {
            lastToken.next = new Token(length, id);
            lastToken = lastToken.next;
        }
        else
        {
            lastToken = lastToken.next;
            lastToken.length = length;
            lastToken.id = id;
        }
    }

    /**
     * Inner class for storing information about tokenized lines.
     */
    public class LineInfo
    {
        /**
         * Creates a new LineInfo object with token = Token.NULL and obj = null.
         */
        public LineInfo()
        {
        }

        /**
         * Creates a new LineInfo object with the specified parameters.
         */
        public LineInfo(byte token, Object obj)
        {
            this.token = token;
            this.obj = obj;
        }

        /**
         * The id of the last token of the line.
         */
        public byte token;

        /**
         * This is for use by the token marker implementations themselves. It
         * can be used to store anything that is an object and that needs to
         * exist on a per-line basis.
         */
        public Object obj;
    }
}
